Adjusting Link Layer Control Frame to Facilitate Data Thoughput

ABSTRACT

A base station subsystem includes logic to change the modulation and coding scheme for radio communications, and logic to communicate with a switching GSM to cause a change in link layer control frame size to reflect the change in modulation and coding scheme.

This application is a continuation of U.S. patent application Ser. No.12/650,475, filed Dec. 30, 2009, now U.S. Pat. No. 8,379,607; which is acontinuation of U.S. patent application Ser. No. 10/965,466, filed Oct.13, 2004, now U.S. Pat. No. 7,664,079; the contents of which are herebyincorporated by reference herein in their entirety into this disclosure.

TECHNICAL FIELD

The present disclosure relates to data communication systems.

BACKGROUND

A popular protocol in use today is the Internet Protocol (IP). IP datapackets may be divided into link layer control (LLC) frames, which arethen divided into radio layer control (RLC) frames. The RLC frames maybe communicated using radio or other wireless technologies. In somesituations the RCL frames may be communicated during one or more radioblock intervals that are fixed in time length. For example, TimeDivision Multiple Access (TDMA) technology may employ radio blockintervals that are each twenty milliseconds of time.

The LLC frame size is typically fixed, whereas the RLC frames may varyin size according to factors such as the modulation and coding schemeemployed.

A problem may arise when communication channel conditions change. Achange in channel conditions may lead to a change in modulation andcoding scheme, which may in turn affect the number of errorcorrection/redundancy bits provided in RLC framing. Thus, when thefixed-sized LLC frame is encoded into RLC frames, changes to the RLCframe size resulting from the change in modulation and coding scheme mayresult in wasted space in the fixed-size radio control blocks.

SUMMARY

The following summary is intended to highlight and introduce someaspects of the disclosed embodiments, but not to limit the scope of theinvention. Thereafter, a detailed description of illustrated embodimentsis presented, which will permit one skilled in the relevant art to makeand use aspects of the invention. One skilled in the relevant art canobtain a full appreciation of aspects of the invention from thesubsequent detailed description, read together with the figures, andfrom the claims (which follow the detailed description).

A base station subsystem includes logic to change the modulation andcoding scheme for radio communications, and logic to communicate with aswitching GSM to cause a change in link layer control frame size toreflect the change in modulation and coding scheme. The link layercontrol frame may be one of multiple frames representing an InternetProtocol data packet. A change in communication channel conditions maycause the change in modulation and coding scheme. The change in channelconditions may include a change in channel bit error rate and/or achange in channel noise level.

BRIEF DESCRIPTION OF THE DRAWINGS

The headings provided herein are for convenience only and do notnecessarily affect the scope or meaning of the claimed invention.

In the drawings, the same reference numbers and acronyms identifyelements or acts with the same or similar functionality for ease ofunderstanding and convenience. To easily identify the discussion of anyparticular element or act, the most significant digit or digits in areference number refer to the figure number in which that element isfirst introduced.

FIG. 1 is a block diagram of an embodiment of a elements of a network toenable wireless communications.

FIG. 2 is a time line diagram of an embodiment of a wireless dataframing that may adversely affect data throughput.

FIG. 3 is a time line diagram of an embodiment of a wireless dataframing that may mitigate adverse affects on data throughput.

FIG. 4 is a flow chart of an embodiment of a process of adjusting linklayer control frame size to mitigate adverse affects on data throughput.

DETAILED DESCRIPTION

The invention will now be described with respect to various embodiments.The following description provides specific details for a thoroughunderstanding of, and enabling description for, these embodiments of theinvention. However, one skilled in the art will understand that theinvention may be practiced without these details. In other instances,well known structures and functions have not been shown or described indetail to avoid unnecessarily obscuring the description of theembodiments of the invention. References to “one embodiment” or “anembodiment” do not necessarily refer to the same embodiment, althoughthey may.

FIG. 1 is a block diagram of an embodiment of elements of a network toenable wireless communications. A radio base station system (BSS) 102comprises a base transceiver station (BTS) 104, a packet channel unit(PCU) 106, and logic 108. The BSS 102 is coupled to an antenna 114.Herein, logic refers to signals, such as program instructions and/ordata, and/or circuits that affect the operations of a device.

The BSS 102 transmits and receives radio signals to and from devicessuch as cell phones. The BTS 104 interacts with the antenna 114 totransmit and receive these signals. The BTS 104 interacts with the PCU106 to implement modulation and coding schemes on data communicated toor received from the BTS 104. Thus, the PCU 106 adds radio layer control(RLC) framing to communications to the BTS 104, or removes RLC framingfrom communications from the BTS 104.

The BSS 102 is coupled to a switching system 110 comprising logic 112.In some embodiments, the switching system 110 may comprise one or moreSwitching GSM (SGSM) network elements. In other embodiments theswitching system 110 may comprise one or more mobile switching centers(MSCs). The switching system 110 provides link layer control (LLC)framing to Internet Protocol (IP) data packets received from elsewherein the system, and builds IP data packets from LLC frames received fromthe BSS 102.

Over time, communication channel conditions may vary. For example, thecommunication channel may become noisier, resulting in an expectation ofmore errors in received and transmitted frames. In other words, thechannel bit error rate may increase. As a second example, incomingpacket signal strength may decline. As a third example, channel datathroughput may change. Communication channel conditions may also changeby improving, for example, by a decrease in channel bit error rate.

Conditions such as these may be detected by the BSS 102. The PCU 106 inthe BSS 102 may determine that the coding and modulation scheme shouldbe adjusted, which may result in a different size for the RLC frames.

In some embodiments, for example, in Global System for MobileCommunications (GSM) environments using Time Division Multiple Access(TDMA), the RLC frames are communicated within time intervals known as aradio blocks. One or more complete RLC frames may be transmitted withinone radio block. The transmission of an RLC frame will is generally notsplit over two radio blocks. In some cases, the adjustment of RLC sizeresulting from the change in modulation and coding scheme may result insignificant unused time within some radio blocks as a sequence of RLCpackets is communicated. The logic 108 in the BSS 102, potentially byinteracting with the PCU 106, may detect that there is significantunused transmission time to be expected within some radio block timeintervals resulting from the RLC frame size adjustment to be made toaccommodate the new modulation and coding scheme. The logic 108 in theBSS 102 may communicate with logic 112 within the switching system 110,which may result in a change of LLC frame size.

The change in the LLC frame size may result in a changed RLC frame size.The new LLC frame size resulting from the interaction of the BSS 102with the switching system 110 may result in greater use of transmissioncapability by RLC frames in the environment of the adjusted modulationand coding scheme.

FIG. 2 is a time line diagram of an embodiment of wireless data framingthat may adversely affect data throughput. In this embodiment each TDMAradio block (the interval between T0 and T2 is one radio block) has aduration of or very close to twenty milliseconds. The LLC frame, withoutmodulation and coding scheme bits applied, has a duration of less thanone radio block size (in some situations, the time required tocommunicate an LLC frame may span multiple radio block intervals). TheLLC frame is encoded into multiple (in this embodiment, four) RLCframes.

Due to a change in channel conditions, the number of bits added toprovide modulation and coding causes the communication time of the fourRLC frames comprising the LLC frame to exceed the duration of one radioblock. Because the fourth RLC frame does not fit in the radio block,communication of this frame does not commence until the beginning of thenext radio block. Thus, for the period of time between T1 and T2, nodata is communicated, leading to reduced data throughput and reducedcommunication performance.

FIG. 3 is a time line diagram of an embodiment of wireless data framingthat may mitigate adverse affects on data throughput.

In response to a change in RLC frame size resulting from a change inmodulation and coding scheme, a smaller LLC frame size is determined.The RLC coding of the LLC frame fits into a single radio block interval(the time between T0 and T2 is one radio block interval, as before)without substantial unused communication capacity (communication dataspace).

Depending upon the situation, the LLC frame may be reduced so that onceRLC encoded, it fits efficiently into one or more radio blocks. Or, itmay be determined that the LLC frame size is to be increased, thusallowing the RLC encoding to fit efficiently within two or more radioblocks without substantial unused data space. Thus, adjustment of LLCframe size should result in an RLC encoded LLC frame fitting, withlittle unused data space, into an integral number of radio blocks. Datathroughput is improved because substantially all of the radio blockintervals are used to communicate data.

The radio subsystem (e.g. the system comprising the BSS 102) maycommunicate to the switching system 110 a new RLC frame size and/or acalculated new LLC frame size; or the switching subsystem 110 mayperform the calculation of new LLC frame size based on informationprovided by the radio subsystem.

FIG. 4 is a flow chart of an embodiment of a process of adjusting linklayer control frame size to mitigate adverse affects on data throughput.At 402 communication channel conditions are monitored. At 404 a changein communication channel conditions is detected. If at 406 it isdetermined that the change in channel conditions does not affect themodulation and coding scheme, communication channel conditions arefurther monitored.

Otherwise, a new RLC frame size is determined at 408. The RLC frame sizeadjustment to reflect the change to the modulation and coding scheme mayinclude providing additional or fewer error correction and-or redundancybits in the RLC frame. At 410 a new LLC frame size is determined thattakes into account the new RLC frame size. To determine the new LLCframe size and implement it, the base station system and the switchingsystem communicate. Information communicated from a base station systemto a switching system may comprise the RLC frame size, and/or a LLCframe size, and/or information about a modulation and coding scheme.

At 412 the process concludes.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” Words using the singular or pluralnumber also include the plural or singular number respectively.Additionally, the words “herein,” “above,” “below” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Whenthe claims use the word “or” in reference to a list of two or moreitems, that word covers all of the following interpretations of theword: any of the items in the list, all of the items in the list and anycombination of the items in the list.

What is claimed is:
 1. A base station subsystem for enhanced datathroughput, the base station subsystem comprising: a base transceiverstation; a packet channel unit in communication with the basetransceiver station; and a logic in communication with the basetransceiver station, the logic for applying a link layer control framefit into an integral number of radio blocks without unused data space inthe radio blocks, thereby maintaining efficiency of overall datathroughput, and communicating with a switching system to change the linklayer control frame size to reflect the applied link layer controlframe, such that data throughput is enhanced.
 2. The base stationsubsystem of claim 1, further comprising an antenna in communicationwith the base transceiver station.
 3. The base station subsystem ofclaim 1, wherein the logic monitors the communication channelconditions.
 4. The base station subsystem of claim 3, wherein thecommunication channel conditions includes a change in one of channel biterror rate, noise level, and data throughput.
 5. The base stationsubsystem of claim 1, wherein the link layer control frame includes oneof multiple frames representing an Internet Protocol data packet.
 6. Thebase station subsystem of claim 1, wherein the logic determines a newradio layer control frame size to accommodate the change in modulationand coding scheme.
 7. The base station subsystem of claim 6, wherein thelogic communicates at least one of the new radio layer control framesize or a new link layer control frame size to a switching system.
 8. Asystem for enhanced data throughput, the system comprising: a basestation subsystem; a switching system coupled with the base stationsubsystem; a logic on the base station subsystem, the logic for applyinga link layer control frame fit into an integral number of radio blockswithout unused data space in the radio blocks, thereby maintainingefficiency of overall data throughput, and communicating with theswitching system to change the link layer control frame size to reflectthe applied link layer control frame, such that data throughput isenhanced.
 9. The system of claim 8, wherein the switching systemincludes a switching GSM network element.
 10. The system of claim 8,wherein the switching system includes a mobile switching center.
 11. Thesystem of claim 8, wherein the logic monitors the communication channelconditions.
 12. The system of claim 8, wherein the link layer controlframe includes one of multiple frames representing an Internet Protocoldata packet.
 13. The system of claim 8, wherein the logic determines anew radio layer control frame size to accommodate the change inmodulation and coding scheme.
 14. The system of claim 13, wherein thelogic communicates at least one of the new radio layer control framesize or a new link layer control frame size to a switching system.
 15. Amethod for enhanced data throughput, the method comprising: detecting achange in communication channel conditions; and adjusting a link layercontrol frame size to accommodate the change in communication channelconditions, such that overall data throughput remains efficient despitethe change in communication channel conditions; and applying the linklayer control frame fit into an integral number of radio blocks withoutunused data space in the radio blocks.
 16. The method of claim 15,further comprising monitoring the communication channel conditions. 17.The method of claim 15, wherein the change in communication channelconditions includes a change in one of channel bit error rate, noiselevel, and data throughput.
 18. The method of claim 15, wherein the linklayer control frame includes one of multiple frames representing anInternet Protocol data packet.
 19. The method of claim 15, furthercomprising determining a new radio layer control frame size toaccommodate the change in modulation and coding scheme.
 20. The methodof claim 19, further comprising communicating at least one of the newradio layer control frame size or a new link layer control frame size toa switching system.